Composite and nanocomposite materials evaluation and assessment for cryogenic propellant storage

This paper describes the activities performed within the PRORA USV Cryotank technological project, aimed at studying barrier and microcrack resistance optimized composite materials, in order to test their application in LOX cryogenic tank building. The possibility to use carbon fiber reinforced composites based on different matrix systems, thermoset and thermoplastic, was investigated in order to assess the potential advantages of these efficient materials versus the metallic ones. The possibility to use nanocomposite matrices is also analyzed, applied either to the tank structural layer or to a potential internal liner. Nanocomposites sport a series of features that make them very attractive for cryogenic tank manufacturing. Those materials can potentially provide increased stability to the system, by preventing chemical degradation in aggressive liquid fuel environments as well as reduce the coefficient of thermal expansion (CTE) mismatch between the matrix and reinforcing fibers, and, consequently lower the stress free temperature of the composite. The results of mechanical and cryogenic thermal cycling tests on selected composites systems will be presented in this paper, together with the composite tank preliminary design approach. The preparation, optimization and characterization of polymer-layered silicate nanocomposites for liquid oxygen storage will also be reported and discussed, with particular regard to the chemical resistance to oxidation of these materials with respect to the pristine polymer matrices.